Unit 7: Microbes & Diseases 8.L1.1 Summarize the basic characteristics of viruses, bacteria, fungi, and parasites relating to the spread, treatment, and prevention of disease.

8C Microbes and Disease What are microbes? Uses of microbes Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities

What are microbes? Microbes are very small living things and are sometimes called micro-organisms. Microbes are so tiny that they cannot be seen with the naked eye. They can only be seen using a microscope. How many different microbes can you name?

Different types of microbes There are three types of microbes: microbes bacteria viruses fungi

Bacteria fact file Bacteria Found everywhere, in the air, soil, water, inside your body and on your skin. e.g. Salmonella and Streptococcus size: 1/1000 mm very small shape: Bacteria can be spherical, rod-shaped or spiral or corkscrew. Usually classified by its shape. structure: Bacteria are single-celled organisms, which do not completely have a nucleus. Some cause disease, but many are useful. reproduction: Bacteria reproduce very quickly. They tend to multiply very rapidly under favourable conditions, forming colonies of millions or even billions of organisms within a space as small as a drop of water.

Bacterium structure

Viruses fact file Viruses MUST HAVE A HOST CELL e.g. flu virus and HIV (the AIDS virus), chicken pox, viral meningitis, Ebola. size: 1/1,000,000 mm shape: Viruses have regular and geometric shapes. structure: A virus is a simple organism which does not display ALL the characteristics of living things. They are made up of a protein coating and some genetic material. reproduction: Viruses can only grow and reproduce within other living things.

Virus structure

Fungi fact file Fungi e.g. Penicillium and yeast size: Some fungi can actually be seen with the naked eye, others are slightly bigger than bacterial cells. shape: Fungi come in many different shapes. structure: Fungi have the most complex structures of all the microbes. They feed off other living things.

Fungi (yeast) structure

8C Microbes and Disease What are microbes? Uses of microbes Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities

8C Microbes and Disease What are microbes? Uses of microbes Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities

Microbes can cause disease The diseases caused by microbes and their severity depend on the type of microbe. viruses bacteria fungi influenza (flu) food poisoning fungal sinusitis mumps sore throats athlete’s foot chickenpox tuberculosis (TB) Onychomycosis (causes discoloured toe nails) smallpox tetanus polio cholera rabies typhoid German measles whooping cough viral meningitis bacterial meningitis

Which type of microbe?

How do microbes enter the body? Microbes can enter the body in many different places. eyes ears nose mouth skin genitals cuts How are the diseases caused by microbes spread?

How are microbes spread? The spreading of microbes and disease is known as transmission. A cough or a sneeze can release millions of microbes into the air which can then infect somebody else. 1. Transmission by air Dirty water can transmit many diseases, e.g. cholera, which can be transmitted by drinking. 2. Transmission by water

How are microbes spread? An animal can carry a microbe from one place to another, e.g. a mosquito which spreads the malaria parasite. 3. Transmission by animals Many microbes can be exchanged from one person to another by direct or indirect contact: 4. Transmission by contact direct contact by hand; indirect contact, e.g. by walking on a wet floor already contaminated by someone else who has athlete’s foot; sexual contact.

How are microbes spread? There are other forms of indirect contact, e.g. the transmission of microbes from mother to unborn child. 4. Transmission by contact If the mother develops the HIV/Aids infection, it can be passed on to the unborn child through the placenta. Transmission through the placenta Transmission via breastfeeding If a child is being breastfed, he or she can also pick up microbes from the mother via the mother’s milk.

How is the spread of disease stopped? The spread of disease can be prevented by making sure that good hygiene is used in key places such as bathrooms and kitchens. Chemicals called antibiotics can be used to treat bacterial infections. People can be immunized against some diseases (viruses) by the injection of a vaccine.

8C Microbes and Disease What are microbes? Uses of microbes Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities

Fighting microbes How does the body fight off microbes that cause disease?

What do white blood cells do? The human body has a number of natural defences against microbes. Noses are hairy inside to trap microbes! white blood cell The body also produces white blood cells to help defend it from microbes. Some white blood cells can destroy microbes by engulfing them. antigen antibody Some white blood cells are able to produce chemicals called antibodies. These pairing with matching antigens on the surfaces of microbes and so help the white blood cells to engulf microbes.

8C Microbes and Disease What are microbes? Uses of microbes Contents 8C Microbes and Disease What are microbes? Uses of microbes How microbes cause disease Fighting disease Summary activities

Glossary antibiotics – Chemicals prescribed as medicine to kill bacteria inside the body. antibodies – Chemicals produced by white blood cells to fight microbes that cause disease. bacteria – The type of microbes that are single-celled organisms. fungi – The type of microbes that feed off other living things. immune – Resistance to infection caused by a microbe. microbe – A very small living thing. transmission – The spread of a disease from person to person. viruses – The type of microbes that can only grow and reproduce within other living things.